workqueue: Fix missing kfree(rescuer) in destroy_workqueue()

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Qian Cai <cai@lca.pw>
Fixes: def98c84b6cd ("workqueue: Fix spurious sanity check failures in destroy_workqueue()")
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 93e20f5..3f067f1d 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -4345,6 +4345,7 @@
 
 		/* rescuer will empty maydays list before exiting */
 		kthread_stop(rescuer->task);
+		kfree(rescuer);
 	}
 
 	/* sanity checks */